THE BUTTERFLY: STRUCTURE OF THE LEGS. 43 



scales, rendering it opaque, while the lower layer receiACS less of this deposit 

 and is consequently a little more transparent. Whence it follows that the 

 colors of the scales as a whole are more vivid upon their upper than u])on 

 their under surface. Tlie changeable and irridcscent colors of some butter- 

 flies, on the other liand, which are seen far more rarely in l)utterflie8 of the 

 temperate regions than in those of the tr()[)ics, are not due in any sense to 

 a pigment but solely to the reflection of the light from the fine impressed 

 striae upon the scales. As a general rule the scales peculiar to the male 

 sex haAC little or no color, but there are some exceptions, as in the various 

 species of Argynnis and its allies, where the basal portion of the scales is 

 of a deep black color. While colorless scales, excepting such as occur in 

 the vitreous spots upon the surface of the wing of some buttei-flies, are other- 

 wise of comparatively rare occurrence. 



The jmtayia are slender, small pieces of membrane, curving around the 

 anterior base of the fore wings and connected with the trunk by a slender 

 attachment just in front of the wings ; the portion in front of the wings is 

 very short, the main part being applied to the upper surface of the base of 

 the wings, and often extending to a considerable distance posteriorly ; thev 

 ser\ e to protect the hinge of the wings from injury and are densely covered 

 with scales or hairs or both ; there are none in front of the hind wings. 



The legs (52-60), as in all true insects, are six in number, one pair to 

 each division of the thorax. They are invariably very slender and agree 

 in their parts and generally in their proportions, although not minutely. 

 As we ascend the structural scale, however, the front pair becomes more 

 and more atrophied, first in one sex, afterwards in both, as will be hereafter 

 detailed. The leg is comijosed of five distinct portions : coxa, trochanter, 

 femur, tibia and tarsi. The coxae, or haunches, are usually pretty well 

 developed, sometimes, as in the Papilioninae, very prominent, serving in 

 their connate obpyramidal form — connate both as regards the opposing and 

 the neighboring pairs — as excellent bases of attachment for the movable 

 parts of the leg ; they extend obliquely doAvnward and backward and form 

 a strong support to the hinder part of the thorax, which is the centre of 

 gravity of the whole body. The trochanters are inconspicuous small glolni- 

 lar masses at the tips of the coxae, carrying the base of the femora a little 

 outward, and serving for greater freedom of motion in all the succeeding 

 parts. T\\(i femora or thighs are long and slender, straight but somewhat 

 gibbous, compressed, stick-like members, largest near the base, and when 

 in position placed at a very sharp angle Avith the coxae, which they almost 

 always exceed in length ; they are the stronger parts of the movable legs, 

 their gibbous form fjivimj room for a considerable amount of muscular 

 tissue ; they are always unarmed, but generally densely clothed with scales 

 and not infrequently with an inferior heavy fringe of long hairs. The tihiae 

 or shanks are slender, straight, equal, cylindrical or tetraquetral members, 



